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# An airplane with an airspeed of 64 km/h lands on a runway where the wind speed is 40 km/h . What is its landing speed if its tailwind ?

Ive attempted to do this by adding and got the answer 104 km/h but the hw keeps saying Im wrong. So how would i go about solving this one ? Any and all help would be appreciated!

### 3 Answers

- derframLv 73 weeks ago
The question doesn't specify *which* speed they are looking for. With a landing airspeed of 64 km/h and a tailwind of 40 km/h, the landing *GROUND SPEED* will indeed be 104 km/h. But the landing *AIR SPEED* will still be 64 km/h. Perhaps that is the answer they are after.

- Andrew SmithLv 73 weeks ago
104 is correct for the question as asked. But in a comment you say to round to TWO significant figures. That is inappropriate given the information in the question. 104 km/hr is correct. 1.0 * 10 ^ 2 is the answer rounded to 2 significant figures. But adding and subtracting requires maintaining the least accurate decimal place. ie the units column. So you SHOULD keep all the figures accurate to the units column. Either the question is wrong or the computer answer is wrong.

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- GTBLv 73 weeks ago
if the tailwind is of the identical direction as is the aircraft, the 104 km/hr answer should be correct; did you omit anything in your submission to this forum (like the tailwind was at an angle of x degrees to the direction of the aircraft)?

Not that i see, the question doesn't list a specific direction. All it says is "What is its landing speed if the wind is a tailwind, coming from behind the plane?" but at the corner of the screen it says to "make sure i round to 2 significant figures in the last step" so idk what to do?

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I agree with your argument. All speeds should be relative to some frame of reference. We are used to it being the earth so tend to assume that is what they meant. But who knows.